Not sure you can do that. What you can do, however, is move the deploy directory from within to some place else. In that case, make a configuration change in /conf/jboss-service.xml as to where deploy is located before starting JBoss.
That sounds complicated. Because the libraries would be in one place and the config files and deployed jars in another.
I'm trying to come up with a solution for version controlling our project. It'd be nice to have EVERYTHING for the project in one place, instead of split up. With WebLogic you can do this (put the server directory anywhere) and I think that's a very nice feature.